Starting strip for electric discharge devices



9 J. FORCE 9 ,854

STARTING STRIP FOR ELECTRIC DISOWGE- DEVICES Filed April 6, 1946 INVENTOR JONATHAN FORCE BY HIS ATTORNEY Patented Dec. 20, 1949 STARTING s'rarr FOR ELECTRIC DISCHARGE DEVICES Jonathan Force, Cleveland signor to General Electric tion of New York Heights, Ohio. as- Company, a corpora- Application April 6, 1946, Serial No. 660,093 7 Claims. (01. 176-422) This invention relates to electric discharge devices of the type employing ionizable mediums such as gases or vapors, and more particularly to improvements in the type of starting strip used thereon.

Heretoiore starting strips were used to counteract the electrostatic effect of the wall charges on the interior of the gas discharge envelope and to produce distortion of the potential distribution or electrostatic fields between the terminals in order to facilitate starting of the discharge.

In devices employing a hot and glowing fila mentary electrode, the distortion of the field is due particularly to selective adsorption of certain ions or by electrons clinging to the wall of the envelope. The starting strip neutralizes and prevents the wall charge and in turn eliminates one of the causes of unsatisfactory lamp operation. These starting strips were usually thin coatings of conductive substances such as bronze or aluminum paint which frequently by rubbing or by an abrasion action wiped or wore off, thus destroying the continuity of the starting strip.

An object of my invention is to provide new and improved conductive starting strips for controlling electric discharge device operation.

Another object of my invention is to provide a new and improved composition to be used as a conductive starting strip for electric discharge devices which will adhere firmly to the glass wall of the envelope.

A further object of my invention is to provide a new and improved composition embodying a fritting agent which will adhere firmly to the glass wall of the envelope of a fluorescent lamp at temperatures below the glass fusion point.

A still further object of my invention is to provide a method of forming a conductive starting strip on a vitreous envelope of an electric discharge device..

Further features and advantages of my invention will appear from the following detailed description of species thereof.

In the drawing, Fig. 1 is a side elevation, partly in section, of a positive column discharge device l illustrating my invention. The device I shown therein comprises an elongated tubular or cylindrical envelope 2 having sealed into the ends thereof lead-in wires 3', l and 5, B electrically connected to the thermionic electrodes 1 and B respectively. Suitable provision may be made, not shown, for connecting these leadstarting and maintaining the gaseous discharge ing-in wires to a source of electrical energy for 55 between two electrodes and also for heating the electrodes if necessary, whereby they are brought to a glowin and emitting temperature. Electrodes 1 and 8 comprise a coil (preferably a coiled coil of wire such as tungsten coated with a material of high electron emissivity, such as an alkaline earth oxide like barium or strontiumoxides or mixtures theerof). The envelope 2 contains a gaseous atmosphere such as a rare gas like kyrpton, neon, argon, or mixtures thereof or a vaporizable metal such as mercury, or a mixture of a gas and vaporizable metal. A quantity of mercury which may be in excess of that vaporized during operation of the device is indicated by a drop 9 inside the envelope 2. The device i may be a low pressure positive column lamp of the fluorescent type having a suitable phosphor In on the surface of the envelope 2, which under the influence of radiation produced by an electric discharge within the envelope, excites the phosphor to produce fluorescence. 0n the outside of the envelope 2 and terminating near ends thereof I provide a starting strip ll of conductive composition and comprising an ingredient to effect adherence to the glass. More particularly, I provide a composition for use with a vitreous envelope which after application to the envelope, and after suitable heat treatment, results in a stronglyadherent vitreous film containing metallic particles on the surface of the envelope, and which I have found to have a longer life and improved qualities which resist wearing, brushing, and deterioration encountered during ordinary and rough usage. This starting strip may be inside or outside of the glass receptacle and means may be provided for connecting it to one or both of the electrodes: 1 and 8.

In accordance with an object of my invention, I provide a conductive composition to be used as a starting strip which will adhere firmly to the glass envelopes at temperatures well below the glass fusion point. Accordingly, I provide a composition for application to a vitreous envelope and which comprises a reducible metallic compound and a compound which serves to produce after heat treatment a closely adherent and evenly dispersed metallic layer or strip. Briefly stated, I prefer to use a reducible metallic compound of the metals in groups 1 and 8 ofthe periodic table such as silver oxide, platinum chloride or reducible compounds of gold and rhodium and the like, and a compound such as lead borate which during the heat treatment 7 ance 'of the strip being determined by the specific resistivity and the dimensions of the strip.

In the mixing of the composition prior to application to the envelope and heat treatment thereof, I have found that one way in which 'the metallic compound may be reduced during the heat treatment is by the inclusion of a suitable reducing agent such as glycerin, citric acid, tartaric acid, polymerized formaldehyde, aluminum formate, sugar, or dextrin. A suitable diluent such as methyl alcohol may be added to vary the viscosity of the composition.

Generally speaking, I efiect these desired results by means of a compound comprising ingredients which when combined together in the right proportions and applied to a glass envelope frits together andto the glass attemperatures from 500 to 550 degrees centigrade. Forexample, this conductive substance may be a paste containing 1050 grams of silver oxide, 600 cubic centimeters of methyl alcohol, 840 cubiccentimeters of glycerin, and 450 grams of lead borate. The lead borate is used as the fritting agent. It irits to the glass envelope at temperatures below the glass fusion point and forms a porous body through which the reduced metal is dispersed. Thus a conductive and abrasive resistant path is obtained which by rubbing or abrasive action will not wipe or wear on, and by this means secure the continuity of the starting strip. Generally speaking the resistance of this starting strip is of a low ohmic value usually 25 to 100 ohms.

Application of this composition to the glass envelope 2 may be perfected either before or after the envelope is coated with phosphor and may be applied in any of the well known'methods such 1 as painting, squirting the material from a nozzle, or applying by means of a thin rubber roller. The viscosity, thickness, or stickiness of the composition may be varied to fit the type of application by means of a suitable diluent such as methyl alcohol.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electric discharge device of the type employing an ionizable medium, the combination comprising a vitreous envelope, a plurality ofelectrodes therein, and an abrasive resistant starting strip closely adherent to the vitreous envelope and comprising a layer of lead borate fritted to said envelope and containing evenly distributed metallic particles in physical contact giving to said starting strip a predetermined electrical resistance.

2. In combination, an electric discharge device 3. In combination, an electric discharge device of the type employing an icnizable medium and a vitreous envelope, a plurality of electroda therein, and a starting strip comprising lead borate adherent to the vitreous envelope and containing evenly distributed particles of platimnn in physical contact giving to said starting strip a predetermined electrical resistance.

4. In combination, an electric discharge device of the type employing an ionizable medium and a vitreous envelope, a plurality of electrodes therein, and a starting strip comprising lead borate adherent to the vitreous envelope and containing evenly distributed particles of rhodium in physical contact giving to said starting strip a predetermined electrical resistance.

5. The method of forming a conductive starting strip on a vitreous envelope of an electric discharge device which comprises forming a paste of the type employing an ionizable medium and a vitreous envelope, a plurality of electrodes therein, and a starting strip comprising lead 'borate adherent to the vitreous envelope and containing evenly distributed particles of silver in physical contact giving to said; starting strip a predetermined electrical resistance.

of reduciblemetallic compound, lead borate, and a reducing agent, applying said paste to the envelope, subjecting said envelope and paste to a temperature suiiicient to eiiect reduction of said compound to particles of the corresponding metal and to frit the lead borate to the envelope in order to form a closely adherent layer thereof 'closely adherent layer thereof containing metallic particles of silver in physical contact giving to said starting strip a predetermined electrical resistance.

7. The method of forming a conductive starting strip on a vitreous envelope of an electric discharge device which comprises iorming a paste of platinum chloride, lead borate, applying said paste to the envelope, subjecting said envelope and paste to a temperature sufiicient to elect reduction of said compound and to frit the lead borate to the envelope in order to form a closely adherent layer thereof containing metallic particles of platinum in physical contact giving to said starting strip a predetermined electrical resistance. p

JONATHAN FORCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

